ci: update integration test logic

[jackwotherspoon]

Pull request from forks once merged will still be skipped github.event.pull_request.head.repo.full_name will still be that of the fork.

To combat this we run the job on all events that are not a pull_request (aka schedule and push)

[enocom]

A comment explaining why we're doing this would be nice for future readers.

Also, bonus points if we can split this across multiple lines to make it more readable.